Leishmaniasis is a parasitic disease that is found in parts of the tropics, subtropics, and southern Europe. It is classified as a neglected tropical disease (NTD), affects nearly one million people per year, and can be fatal if left untreated. Leishmaniasis is caused by infection with Leishmania parasites, which are spread by the bite of infected sand flies. There are several different forms of leishmaniasis in people. The most common forms are cutaneous leishmaniasis, which causes skin sores, and visceral leishmaniasis, which affects several internal organs. Known treatments for leishmaniasis include amphotericin B, a combination of antimonials and paramomycin, and miltefosine, with each having its own efficacy, advantages, and disadvantages.
In the field of natural products, compounds from the terrestrial realm have represented much of the literature due to the accessibility of plants and their use in traditional medicine. It was not until the 1950s that the concept of “drugs from the sea” would begin to gain momentum, at least partly due to advancement in collection techniques, i.e., SCUBA diving. Marine sponges have proven a rich source of secondary metabolites among the Antarctic invertebrates. Many of these secondary metabolites are bioactive, with some causing feeding deterrence in ecologically relevant predators and some displaying potent antimicrobial or cytotoxicity properties. The bright yellow Antarctic cactus sponge, Dendrilla membranosa Pallas (family Darwinellidae, order Dendroceratida) is a dominant demosponge that prior studies have shown is rarely preyed upon and deters feeding against amphipods, the principal mesograzers of the Western Antarctic Peninsula (WAP). Along the WAP, macroalgal forests dominate the shallow benthos and colorful invertebrates cover stunning walls that drop straight to the ocean floor. The chemical ecology of the current benthic marine invertebrate fauna is largely ancient and endemic. The diversity rivals that of temperate and tropical climates, though key differences in ecology dictated by physical pressures such as the Antarctic Circumpolar Current (ACC) and repeated periods of glaciations have sculpted a unique environment.
Diterpenes have been isolated from sponges of the orders of Dendroceratida and Dictyocertida. D. Membranosa collected from McMurdo Sound, Antarctica, has been shown to yield highly oxidized diterpenes, including gracilin derivatives, and the aromatized diterpene membranolide A (Molinski T F et al., J. Org. Chem., 1987, 52:296-298; Manriquez V et al., Acta Crystallogr. Sect. C, 1990, 46:2486-2487; Puliti R et al., Acta Crystallogr. Sect. C, 1993, 49:1373-1376; Baker B J et al., J Nat. Prod., 1995, 58:1459-1462; and Fontana A et al., J. Nat. Prod., 1997, 60:475-477). The isolation of membranolide-type diterpenes from D. membranosa collected from Palmer Station on Anvers Island, Antarctica, has been reported (Ankisetty S et al., J. Nat. Prod., 2004, 67:1172-1174).